ProjectSummary Melanomaisadevastatingdisease,withfive-yearsurvivalratesformetastaticdiseaseunder15%.Exciting newtherapieshaveemergedforBRAF-mutantmelanoma,butNRASmutantmelanomacontinuestohave poor prognosis and limited therapeutic options. Even with the newest targeted- and immuno-therapies, a largepercentofpatientsdoesnotbenefitand/orexperiencediseaseprogression.Inparticular,the~30% of melanoma patients whose tumors have mutations in the NRAS oncogene, and those who become re- sistanttocurrenttherapies,havelimitedtreatmentoptionsandpoorprognosis.Developingeffectivethera- pies for NRAS mutant melanoma and overcoming resistance to BRAF/MEK inhibition is of utmost im- portanceinmelanoma. IdentifyingvulnerabilitiesinNRAS-drivenmelanomasiscriticaltodesigneffectivetreatmentsforthisclass oftumors,astherearecurrentlynodrugstodirectlyinhibitmutantNRAS.MutationsintheTERTpromoter, (thecatalyticsubunitofTelomerase)arefoundinapproximately70%ofmelanomas,constitutingthemost frequent genetic alteration in this cancer. Preliminary studies by our team indicate that melanomas are highlyaddictedtoTERT,asdepletionorinhibitionofTERTcausesstrikingandrapidapoptosis.Thesedata supportthehypothesisthatTERTplaysacriticalroleinmelanomaandconstitutesacompellingtar- getfortherapy.ThegoalofthisproposalistoestablishtheefficacyoftargetingTERTinmelanoma,alone andincombinationwithotherpromisingtherapies.Acorollaryofthisgoalistodissectthecontributionof TERTtomelanomasurvivalandprogression.InAim1,weproposetosystematicallydissectthecontribu- tion of TERT?s telomere-dependent and -independent roles for melanoma progression and survival, with particularfocusonNRAS-mutantmelanoma,whichisinurgentneedofnewtherapies.Todatenogroup hassystematicallyexploredTERTinhibitioninmelanomapre-clinicalandpatient-derivedxenograftmodels, particularly in combination with other therapies. In Aim 2 we will address this gap in knowledge by as- sessingtheefficacyofcombiningnovelTERT-basedapproacheswithpromisinganti-melanomatherapies, includinginhibitorsofmitochondrialmetabolismandimmunotherapies.Weexpectthattheproposedwork will enable us to: i) Mechanistically determine the contribution of telomere-dependent and telomere- independent functions of TERT in melanoma;? ii) Develop novel combination strategies for NRAS mutant melanomaandmelanomasresistanttotherapy;?iii)Provideactionableinformationthatwillguidethedesign ofnovel,TERT-basedcombinationtherapiesaimedatpreventingandovercomingdrugresistance,anden- hancing the durability of responses and survival benefits for melanoma patients. Additionally, we expect thatourstudieswillpavethewayfornoveltreatmentsforothercancerswithTERTand/orRASmutations, heighteningthepotentialimpactofourproposal.